The present disclosure relates generally to intraocular pressure/flow control systems and methods for treating a medical condition. In some instances, embodiments of the present disclosure are configured to be part of a system for the treatment of ophthalmic conditions.
Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. The tissue pressure of the intraocular contents is called the intraocular pressure (IOP). In general, vision loss from glaucoma results when the IOP increases to pressures above normal for prolonged periods of time. IOP can increase due to high resistance to the drainage of the fluid relative to its production. As the outflow facility decreases, the IOP increases for a given aqueous humor production rate. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision.
The eye's ciliary body continuously produces aqueous humor, the clear fluid that fills the anterior segment of the eye (the space between the cornea and lens). The aqueous humor flows out of the anterior chamber (the space between the cornea and iris) through the canalicular (i.e., conventional) and the uveoscleral pathways, both of which contribute to the aqueous drainage system. Any impairment to the drainage of aqueous humor through these outflow pathways can influence the IOP of the eye.
FIG. 1 is a cross-sectional diagram of the front portion of an eye 10 that helps to explain the processes of glaucoma. In FIG. 1, representations of the lens 110, the lens capsule 112, the cornea 120, the iris 130, the ciliary body 140, the trabecular meshwork 150, Schlemm's canal 160, the collector channels 162, the anterior segment 165 including both the anterior chamber 170 and the posterior chamber 175, the posterior segment 178, the sclera 180, the retina 182, the choroid 185, the limbus 190, the suspensory ligaments or zonules 195, the suprachoroidal space 200, the conjunctiva 202, and the scleral spur 203 are pictured. Aqueous fluid is produced by the ciliary body 140, which lies beneath the iris 130 and adjacent to the lens 110 in the anterior chamber 170 of the anterior segment of the eye. This aqueous humor emerges from the ciliary processes 145, washes over the lens 110 and iris 130, and flows to the drainage systems located in the irideocorneal angle 204 (delineated by the dashed lines and bounded by the iris 130 and the cornea 120) of the eye 10.
After production by the ciliary body 140, the aqueous humor may leave the eye by several different routes. Some goes posteriorly through the vitreous body in the posterior segment 178 to the retina, while most circulates in the anterior segment 165 to nourish avascular structures such as the lens 110 and the cornea 120 before outflowing by two major routes located in the irideocorneal angle 204 of the eye 10: the trabecular or conventional trabecular outflow pathway 205 and the uveoscleral or nonconventional outflow pathway 210. The uveoscleral pathway 210 refers to the aqueous humor leaving the anterior chamber 170 by diffusion through intercellular spaces among ciliary muscle fibers. The trabecular outflow pathway 205 is the main route of outflow, accounting for a large percentage of aqueous egress. The route extends from the anterior chamber angle (formed by the iris 130 and the cornea 120), through the trabecular meshwork 150, into Schlemm's canal 160. The trabecular meshwork 150, which extends circumferentially around the anterior chamber 170, is commonly implicated in glaucoma. Among different types of glaucoma, most of those known as open-angle glaucomas are caused by an increase in the resistance to aqueous humor drainage through the trabecular meshwork and/or Schlemm's canal. The trabecular meshwork 150 seems to act like a filter, restricting the outflow of aqueous humor and providing a back pressure that directly relates to IOP. Schlemm's canal 160 is located just peripheral to the trabecular meshwork 150. Schlemm's canal 160 is fluidically coupled to the collector channels 162, thereby allowing aqueous humor to flow out of the anterior chamber 170 and into the bloodstream. After crossing the trabecular meshwork 150, the aqueous humor reaches Schlemm's canal 160 and the collector channels 162. The arrows A1 show the flow of aqueous humor from the ciliary muscle 140, over the lens 110, over the iris 130, through the trabecular meshwork 150, and into Schlemm's canal 160 and the collector channels 162 (to eventually reunite with the bloodstream in the aqueous veins 206 and episcleral vessels 207).
One method of treating glaucoma includes enhancing aqueous outflow. Several current treatments involve the use of ocular drainage implants that may lack long-term efficacy due to fibrosis at the drainage site or system malfunction. The system and methods disclosed herein overcome one or more of the deficiencies of the prior art.